Precise measurement of electrical power consumption is a topic of great interest in any industry or technology that consumes electrical power. Due to the cost of purchasing electrical energy and the environmental impact of various forms of electrical power generation, many businesses and individuals have a strong interest in monitoring electrical power usage. In one simple configuration, a single electrical power meter measures the total electrical power consumption of a single site such as an entire house or building. One problem with the simple configuration is that the single power meter does not directly distinguish the individual devices on the site that consume electricity. Thus, extra information is required to determine the activity and power consumption characteristics of different electrical devices in the site to identify the contributions of individual devices to the total power consumption at the site. In another configuration, multiple power meters can be connected to monitor individual devices in a site. While the approach of using multiple power meters enables monitoring of individual devices, the added cost and complexity of installing and operating the power meters presents an obstacle to efficient measurement of electrical power consumption.
One method of power monitoring that can measure the power consumption of individual devices without requiring separate electrical power meter for each device in a site is referred to as non-intrusive load monitoring (NILM). A NILM system identifies individual electrical devices that consume power from a single electrical source, such as a main electrical line that supplies electrical power to a building. In a NILM system, a single electrical power monitoring device generates information about the power consumption of multiple devices over time, and the NILM system can identify times at which an individual device is activated, deactivated, and the total power consumption of the individual device while activated.
In order to identify each individual device that draws electrical power from a single electrical line, individual electrical waveforms for each device are generated and stored in a memory in the NILM system. An existing NILM system “learns” new devices through a supervised process, referred to as a training stage, where an operator activates and deactivates a new electrical device at predetermined times and the NILM system records the electrical characteristics of the new device. In some configurations, other devices that draw electrical current from the main electrical line should not change between an activated and deactivated state during the supervised learning process to prevent the NILM system from recording erroneous data during the supervised learning process. The supervised learning process increases the difficulty in using NILM systems and may be impractical in environments where one or more electrical devices activate and deactivate during the learning process. Thus, improvements to NILM systems that enable identification of individual electrical devices without a supervised learning process would be beneficial.